The present invention is generally related to telecommunications, and in particular to data transmission across different types of computer networks.
A need exists to efficiently transmit Token Ring packets on an Ethernet network. Token Ring is a well established protocol which enjoys wide usage. One drawback of Token Ring networks compliant with the IEEE 802.5 standard is lack of bandwidth. In particular, Token Ring networks operate at 4 or 16 Mbps in comparison with more recent technologies such as Fast Ethernet, Fiber Distributed Data Interface ("FDDI") and Asynchronous Transfer Mode ("ATM") networks. One way to extend the useful life of existing Token Ring networks is to integrate such networks with other networks such as Fast Ethernet, FDDI and ATM in a manner which takes advantage of the increased bandwidth of those other networks.
Technology for transmission of data across different types of computer networks is known. For example, U.S. Pat. No. 5,535,373, entitled PROTOCOL-TO-PROTOCOL TRANSLATOR FOR INTERFACING DISPARATE SERIAL NETWORK NODES TO A COMMON PARALLEL SWITCHING NETWORK, issued to Olnowich describes translation of data units from a first network protocol to a second network protocol. Initially, the network operating system protocol of the sending network is identified. The data unit is then modified based upon known characteristics of the sending network operating system protocol such that the data unit is placed in a format that can be handled by equipment in the receiving network. However, such data unit translation requires intensive computations, and hence necessitates the use of relatively sophisticated and costly electronic hardware. Further, since some network operating system protocols are proprietary, the technique for making the translation may change each time the operating system protocol is changed, thereby necessitating development and distribution of updated translation tools.
It is also known to encapsulate a first data unit of a first protocol inside a second data unit of a second protocol. To encapsulate a Token Ring packet in an Ethernet packet, the entire Token Ring packet including both header information and payload is stored in the information field of the Ethernet packet. Header information for the Ethernet packet, such as source and destination addresses, must then be determined for the Ethernet packet. However, encapsulation has the disadvantage of producing a relatively large packet because a minimum of 16 bytes are added.
With regard to transmission of Token Ring packets on an Ethernet network, a commercially available product known as "VG-AnyLAN" supplied by the Hewlett-Packard Corporation is known to exist. However, VG-AnyLAN does not allow coexistence of Token Ring packets and Ethernet packets on the same network segment.